binder: Convert binder_alloc selftests to KUnit

binder: Convert binder_alloc selftests to KUnit

Convert the existing binder_alloc_selftest tests into KUnit tests. These
tests allocate and free an exhaustive combination of buffers with
various sizes and alignments. This change allows them to be run without
blocking or otherwise interfering with other processes in binder.

This test is refactored into more meaningful cases in the subsequent
patch.

Signed-off-by: Tiffany Yang <ynaffit@google.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Link: https://lore.kernel.org/r/20250714185321.2417234-6-ynaffit@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>